In using interphones, a remote monitoring function of the interphone may be used to monitor conditions around the target interphone so as to take corresponding actions in occasions that, for example, a call initiating party (who has a corresponding manager privilege) wants to know conditions of the called party, i.e., the monitored side, without being noticed when the called party does not respond to the call; or a missed or stolen interphone needs to be found; or a target interphone used by a user who is in danger needs to be tracked in real time.
For this remote monitoring function, the initiator transmits a remote monitoring instruction to the target interphone; the target interphone, after receiving the remote monitoring instruction, activates a microphone and a push to talk (PPT) button automatically, and meanwhile initiates a secret call to the sender of the instruction automatically for a certain time period, without any transmitting indication on the target interphone, so the target user does not know the transmission. In this case, all the sound (voice or background noise) produced around the target interphone is transmitted secretly.
The implementation procedure according to the existing interphone remote monitoring technique is as follows. A monitored time period (i.e., a transmit time) of the target interphone is firstly set via a customer program software (CPS). Then interaction between the monitoring side and the monitored side is performed via a control signaling block (CSBK) based on the digital mobile radio (DMA) protocol. Specifically, a remote user, i.e., the monitoring side, transmits a remote monitoring instruction to a target interphone; the target interphone, after receiving the remote monitoring instruction, replies acknowledgement (ACK) information to the initiator of the instruction, i.e., the monitoring side, starts to transmit secretly for one time for a fixed time period previously set via the CPS, and exits the monitored state when the transmit time expires.
There are at least the following disadvantages in the existing remote monitoring
1. The target interphone exits the monitored state and the whole process ends after the time period during which the target interphone is monitored (i.e., the transmit time) expires. The transmitting cannot be started automatically after a certain time interval and repeated for a certain times. Therefore, it cannot satisfy the requirement that the monitored side needs to automatically report its background to the monitoring side in some application scenarios.
2. The time period during which the target interphone is monitored (i.e., the transmit time) is set to be a fixed time period via the CPS. The set time period cannot be changed when using, and the set time period needed to be changed must be reset via the CPS. It can be seen that the time period for monitoring is not decided by the monitoring side but by the monitored side, which lacks flexibility. In practical application, the monitoring side needs to decide the time period for monitoring the monitored side based on an actual situation.